| 摘要 |
Appts. for prodn. of films with a preferential shrinkage from molten thermoplastic material has a die for extruding a tube of molten thermoplastic material, a pressure pipe for applying an internal pressure to the tube to effect radial expansion, an annular air ring for creating a sheath of air in the for of a sleeve, around the external surface of the tube, after it leaves the die, so as to permit controlled expansion of the dia. of the tube, and to cool the tube, a pair of flattening rollers for receiving and flattening the tube after its passage through the air sheath, and a series of rollers transporting the flattened tube in a longitudinal direction, the velocity of rotation of thes erollers being sufficient to form an elongation zone at an elevated temp. of the film, and a relaxation zone after a decrease in the temp. of the film. Used in packaging. |
